What is computed tomographic colonography?

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Computed tomographic (CT) colonography (virtual colonoscopy) is a procedure that uses CT images to produce pictures of the colon. A physician's computer with specialized software then assembles these pictures into a detailed three-dimensional movie that can show polyps and other abnormalities. Virtual colonoscopy may cause less discomfort and take less time than a traditional colonoscopy. If a polyp is found, it may be removed or a biopsy may be performed using traditional colonoscopy.

CT colonography is a procedure used for the screening of colorectal cancer. The test involves an examination of the colon and rectum using pictures obtained with a CT (CAT) scanner. Prior to the procedure, patients will need to take a preparation to cleanse the colon, such as laxatives and/or enemas. The physician will prescribe a special diet, often clear liquids, for the day prior to the examination.

At the beginning of the test, a small flexible tube will be inserted into the rectum to introduce gas into the colon. The CT scanner takes a series of 2- and 3-dimensional images of the colon and rectum showing any polyps or potential signs of cancer. The scanning procedure itself takes approximately 5 minutes and does not require sedation. If a polyp or other abnormality is discovered during the CT colonography, a colonoscopy will likely be required to biopsy or remove the abnormality. In some situations, patients may be able to have the colonoscopy on the same day.

CT colonography is a method to examine the inside of the colon by reconstructing 3D images produced by taking a series of 2D CT scans of the colon. It is an alternative to colonoscopy performed by a gastroenterologist. The pictures can be saved, changed to give better viewing angles, and reviewed after the procedure, even years later. Also called computed tomography colonography, CT colonography, CTC and virtual colonoscopy.

This answer is based on source information from the National Cancer Institute.

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